HTML5 Canvas笔记——图像合成
2020-05-20 本文已影响0人
没昔
编程展示各种图像的合成效果，效果的名称
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>图像合成</title>
<style>
#canvas {
border: 1px solid cornflowerblue;
position: absolute;
left: 150px;
top: 10px;
background: #eeeeee;
border: thin solid #aaaaaa;
cursor: pointer;
-webkit-box-shadow: rgba(200, 200, 255, 0.9) 5px 5px 10px;
-moz-box-shadow: rgba(200, 200, 255, 0.9) 5px 5px 10px;
box-shadow: rgba(200, 200, 255, 0.9) 5px 5px 10px;
}
</style>
</head>
<body>
<select size="11" id="compositingSelect">
<option value="source-atop">目标图顶部显源图</option>
<option value='source-in'>目标图中显源图</option>
<option value='source-out'>目标图外显源图</option>
<option value='source-over'>目标图上显源图</option>
<option value='destination-atop'>源图顶部显目标图</option>
<option value='destination-in'>源图中显目标图</option>
<option value='destination-out'>源图外显目标图</option>
<option value='destination-over'>源图上显目标图</option>
<option value='lighter'>源图+目标图</option>
<option value='copy'>只显示源图</option>
<option value='xor'>异或组合</option>
</select>
<canvas id="canvas" width="600" height="420">Canvas not supports</canvas>
</body>
<script>
'use strict';
let context = document.getElementById('canvas').getContext('2d'),
selectElement = document.getElementById('compositingSelect');
/**
* 绘制文字
*/
let drawText = () => {
context.save();
context.shadowColor = 'rgba(100, 100, 150, 0.8)';
context.shadowOffsetX = 5;
context.shadowOffsetY = 5;
context.shadowBlur = 10;
context.fillStyle = 'cornflowerblue';
context.fillText('HTML', 20, 250);
context.strokeStyle = 'yellow';
context.strokeText('HTML', 20, 250);
context.restore();
};
//Event handlers……
let windowToCanvas = (canvas, x, y) => {
let bbox = canvas.getBoundingClientRect();
return {
x:x-bbox.left*(canvas.width/bbox.width),
y:y-bbox.top*(canvas.height/bbox.height)
};
};
context.canvas.onmousemove=e=>{
let loc = windowToCanvas(context.canvas,e.clientX,e.clientY);
context.clearRect(0,0,context.canvas.width,context.canvas.height);
drawText();
context.save();
//设置选项即为全局合成属性
context.globalCompositeOperation=selectElement.value;
context.beginPath();
context.arc(loc.x,loc.y,100,0,Math.PI*2,false);
context.fillStyle='orange';
context.stroke();
context.fill();
context.restore();
}
//Init……
selectElement.selectedIndex=3;
context.lineWidth=0.5;
context.font='128pt Comic-sans';
drawText();
</script>
</html>
效果如图：
